1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and method for processing semiconductor substrates. More particularly, embodiments of the present invention relate to monitoring performance of an injection valve configured to vaporize liquid reactant and to provide vaporized reactant to a process chamber.
2. Description of the Related Art
Semiconductor processes, for example chemical vapor deposition (CVD) and atomic layer deposition (ALD), sometimes require one or more vaporized processing liquids. These vaporized liquids are generally generated and supplied to a process chamber via a system of pipes (or “lines”) and vaporizing mechanisms known as a gas delivery system. Typically a separate vaporizing mechanism is provided for vaporizing each processing liquid, and is coupled to a source of processing liquid and a source of carrier gas. Each vaporizing mechanism and processing liquid source combination within a gas delivery system is referred to as a vaporization stage. Although a number of vaporizing mechanisms exist (e.g., bubblers, injection valves, etc.), most conventional gas delivery systems employ a plurality of injection valves for vaporizing processing liquids to be delivered to a process chamber, for example a CVD chamber or an ALD chamber.
A typical injection valve comprises a vaporization region. The vaporization region is coupled to a processing liquid inlet for receiving a pressurized processing liquid, a carrier gas inlet for receiving a pressurized inert carrier gas, and an outlet for delivering a vaporized processing liquid/carrier gas mixture. The processing liquid inlet, by necessity, is small in size so as to maintain a low partial vapor pressure of the processing liquid in the carrier gas.
The processing liquid inlet's small size renders the processing liquid inlet susceptible to clogs which result from residue produced when processing liquid reacts with moisture or other contaminants in the gas delivery system. A clogged injection valve can cause downtime not only of the chamber to which the clogged injection valve is coupled, but also of upstream and/or downstream chambers.
To prevent clogging and system downtime caused by clogging, injection valves may be cleaned after in use for a period of time. However, clogging may still happen when cleaning is not performed soon enough while too frequent cleaning increases cost of ownership.
Therefore, there exists a need for apparatus and methods for detecting injection valve clogging and corresponding injection valve cleaning.